The object of this proposal is to solicit funds to help support an international conference entitled THE FOURTH INTERNATIONAL SYMPOSIUM ON BIOLOGICAL REACTIVE INTERMEDIATES: MOLECULAR AND CELLULAR EFFECTS. The dates of the proposed meeting is January 14- 19, 1990, and the site will be Tucson, Arizona. The funds will be used to support travel and maintenance of both foreign and American speakers and chairpeople to Tucson where they will partake in presentations and discussions on the current state of our understanding of reactive intermediates, the chemistry of reactive species and covalent binding, DNA adduct formation and repair, immunotoxicology, oxygen, mycotoxins, pyrollizidine alkaloids, nitrosamines, hepatic and non-hepatic toxicity, and human disease related to reactive metabolites. Emphasis will be placed on the role of molecular targets (protein and DNA), and on the importance of cell-cell interactions in the development of tissue lesions. The program will include a series of invited speakers and several sessions at which volunteer presentations can be made in the form of poster sessions.